Try going into the PS3 Game Data folder and delete everything there for Gran Turismo 5 then try running things again. The system should re-install the data it needs as well as have to try re-downloading the game update.

NO, do not turn it off. Let the system do its thing and relax for a bit. Then, once its done, give the eject button one more go at getting the disc out. As I mentioned, it will take it some time to delete the files due to the amount of the install it did.

Once it is done, if you still can't get the disc out you will need to contact Sony in regards to repairs.